Annealed alkaline earth metal fluorohalide storage phosphor, preparation method, and radiation image storage panel

Abstract

A method, a storage phosphor prepared by the method, and a storage panel. In the method, a precursor mixture is fired, at a temperature between 700 DEG C. and the melting point of the phosphor, to produce an intermediate product. The precursor mixture comprises a combination of species characterized by the relationship: MFX1-xIz.uMaXa:yA:eQ wherein M is selected from Mg, Ca, Sr and Ba; X is selected from Cl and Br; Ma is selected from Na, K, Rb and Cs; Xa is selected from F, Cl, Br and I; A is selected from Eu, Ce, Sm, and Tb; Q is metal oxide; and 0<z</=1; 0<u<1; 0<y</=0.1; and 0<e<0.1. The intermediate product is then annealed in a slightly oxidizing atmosphere, at a temperature, which is lower than said temperature of firing and between about 400 DEG C. and about 800 DEG C., for a time sufficient to reduce the erase fraction of the resulting phosphor relative to the same phosphor produced by firing in the same manner, but not annealing.

What is claimed is: 
     
       1. A method for preparing a storage phosphor comprising the steps of: firing, at a temperature greater than 700° C., a combination of species including species characterized by the relationship:   MFX.sub.1-z I.sub.z.uM.sup.a X.sup.a :yA:eQ     wherein     M is selected from Mg, Ca, Sr and Ba, and combinations thereof;   X is selected from Cl and Br, and combinations thereof;   M a  is selected from Na, K, Rb and Cs, and combinations thereof;   X a  is selected from F, Cl, Br and I, and combinations thereof;   A is selected from Eu, Ce, Sin, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof; and 0<z<1;   0<u<1;   0<y<0.1; and   0<e<0.1 to produce an intermediate product; and       annealing said intermediate product in a slightly oxidizing atmosphere and at a temperature lower than said temperature of said firing and between about 400° C. and about 800° C., for a time sufficient to reduce the erase fraction (EF) relative to the same phosphor produced without said annealing.   
     
     
       2. The method of claim 1 wherein said slightly oxidizing atmosphere has from about 10 to about 200 parts per million of oxygen. 
     
     
       3. The method of claim 1 wherein said firing is in an atmosphere has from about 10 to about 125 parts per million of oxygen. 
     
     
       4. The method of claim 1 wherein said annealing is at a temperature from about 500° to about 750° C. 
     
     
       5. The method of claim 1 wherein said firing is at a temperature from about 750° to about 950° C. 
     
     
       6. The method of claim 1 wherein said firing is at a temperature from about 800° to about 950° C. 
     
     
       7. The method of claim 1 wherein said slightly oxidizing atmosphere has from about 75 to about 125 parts per million of oxygen. 
     
     
       8. The method of claim 1 wherein said annealing is for a time period of from about 0.5 to about 100 hours. 
     
     
       9. The method of claim 1 wherein said firing and said annealing are each in an atmosphere having from about 10 to about 125 parts per million of oxygen. 
     
     
       10. A method for preparing a storage phosphor comprising the steps of: firing, at a temperature greater than 700° C., a combination of species is characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z.rM.sup.a X.sup.a :yA:eQ:tD:dE     wherein     X is selected from the group consisting of Cl and Br, and combinations thereof;   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sin, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   E is an oxosulfur reducing agent selected from the group consisting of compounds and salts having a moiety or ion of the general formula S j  O k , where j and k are positive integers such that 0.25<j/k<1.0, and combinations thereof;   a+b+c is from 0 to 0.4;   z is from 1×10 -2  to 1;   r is from 1×10 -6  to 0.1;   y is from 1×10 -4  to 0.1;   e is from 1×10 -5  to 0.1;   t is from 0 to 10 2  ; and   d is from 0 to 0.020 to produce an intermediate product; and     annealing said intermediate product in a slightly oxidizing atmosphere and at a temperature lower than said temperature of said firing and between about 400° C. and about 800° C., for a time sufficient to reduce the erase fraction (EF) relative to the same phosphor produced without said annealing.   
     
     
       11. A method for preparing a storage phosphor comprising the steps of: firing, at a temperature greater than 700° C., a combination of species is characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FBr.sub.1-z I.sub.z.rM.sup.a X.sup.a :yEu:eQ:dE     wherein     M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   Q is selected from the group consisting of Al 2  O 3  and SiO 2 , and combinations thereof.;   E is an oxosulfur reducing agent selected from the group consisting of compounds and salts having a moiety or ion of the general formula S j  O k , where j and k are positive integers such that 0.25<j/k<1.0, and combinations thereof;   a+b+c is from 0 to 0.04;   z is from 0.05 to 0.5;   r is from 10 -4  to 0.01;   y is from 1×10 -4  to 0.1;   e is from 1×10 -5  to 0.01; and   d is from 1×10 -4  to 0.020 to produce an intermediate product; and     annealing said intermediate product in a slightly oxidizing atmosphere and at a temperature lower than said temperature of said firing and between about 400° C. and about 800° C., for a time sufficient to reduce the erase fraction (EF) relative to the same phosphor produced without said annealing.   
     
     
       12. A method for preparing a storage phosphor comprising the steps of: firing, in an atmosphere of inert gas and from 0 to about 200 parts per million of oxygen, at a temperature from about 750° C. to about 950° C., combination of species is characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z.rM.sup.a X.sup.a :yA:eQ:tD:dE     wherein     X is selected from the group consisting of Cl and Br, and combinations thereof;   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sm, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   E is an oxosulfur reducing agent selected from the group consisting of compounds and salts having a moiety or ion of the general formula S j  O k , where j and k are positive integers such that 0.25<j/k<1.0, and combinations thereof;   a+b+c is from 0 to 0.4;   z is from 1×10 -2  to 1;   r is from 1×10 -6  to 0.1;   y is from 1×10 -4  to 0.1;   c is from 1×10 -5  to 0.1;   t is from 0 to 10 -2  ; and   d is from 0 to 0.020 to produce an intermediate product; and     annealing said intermediate product, in an atmosphere of inert gas and from about 10 to about 200 parts per million of oxygen, at a temperature lower than said temperature of said firing and between about 400° C. and about 800° C., for a time sufficient to deplete iodide relative to the iodide concentration of said combination of species.   
     
     
       13. The method of claim 12 wherein said annealing is for a time sufficient to deplete iodide to the extent of from 2×10 -4  to 2×10 -2  iodide atoms depleted per formula weight of said combination of species. 
     
     
       14. An annealed storage phosphor consisting essentially of oxygen and a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z-2x.rM.sup.a X.sub.a :yA:eQ:tD:dS     wherein   X is selected from the group consisting of Cl and Br, and combinations thereof;   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sin, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   a+b+c is from 0 to 0.4;   z is from 1×10 -2  to 1;   x is from 1×10 -4  to 1×10 -2  ;   r is from 0 to 0.1;   y is from 1×10 -4  to 0.1;   e is from 1×10 -5  to 0.1;   t is from 0 to 10 -2  ; and   d' is from 0 to 0.020.   
     
     
       15. The phosphor of claim 14 further characterized as the product of: (1) firing at a temperature between about 750° C. and about 950° C. a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z.rM.sup.a X.sup.a :yA:eQ:tD:dE       wherein X, M a , X a , A, Q, D, a, b, c, z, r, y, e, and t have the same meanings as in claim 14,   E is an oxosulfur reducing agent selected from the group consisting of compounds and salts having a moiety or ion of the general formula S j  O k , where j and k are positive integers such that 0.25<j/k<1.0, and combinations thereof, and   d is from 0 to 0.020; to produce a fired product; and     (2) annealing said fired product in an atmosphere having from about 10 to about 200 parts per million of oxygen at a temperature lower than said temperature of said firing and between about 500° C. and about 750° C., for a time sufficient to reduce the erase fraction of resulting said storage phosphor relative to the erase fraction of a storage phosphor produced by said firing and without said annealing.   
     
     
       16. A storage phosphor consisting essentially of a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z-2x O.sub.x.rM.sup.a X.sup.a :yA:eQ:tD:d'S     wherein   X is selected from the group consisting of Cl and Br, and combinations thereof;   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sm, and Tb, and combinations thereof;   Q is selected from the group consisting of BcO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   a+b+c is from 0 to 0.4;   z is from 1×10 -2  to 1;   x is from 1×10 -4  to 1×10 -2  ;   r is from 0 to 0.1;   y is from 1×10 -4  to 0.1;   e is from 0 to 0.1;   t is from 0 to 10 -2  ; and   d is from 0 to 0.020.   
     
     
       17. The storage phosphor of claim 16 further characterized as consisting essentially of a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a C.sub.b Sr.sub.c)FBr.sub.1-z I.sub.z-2x O.sub.x.rM.sup.a X.sup.a :yA:eQ:tD:d'S     wherein   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sm, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2  and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   a+b+c is from 0 to 0.04;   z is from 1×10 -4  to 1;   x is from 1×10 -4  to 1×10 -2  ;   r is from 10 -6  to 0.1;   y is from 1×10 -4  to 0.1;   e is from 1×10 -5  to 0.1;   t is from 0 to 10 -2  ; and   d' is from 0 to 0.020.   
     
     
       18. The storage phosphor of claim 17 wherein A is Eu, r is from 10 -4  to 0.01; t is 0; e is 0.01; z is from 0.05 to 0.5; and a and c are 0 and b is from about 0.001 to 0.04. 
     
     
       19. The storage phosphor of claim 16 further characterized as consisting essentially of a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FBr.sub.1-z O.sub.z-2x O.sub.x.rM.sup.a X.sup.a :YEu:eQ:d'S     wherein   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   Q is selected from the group consisting of Al 2  O 3  and SiO 2 , and combinations thereof;   a+b+c is from 0 to 0.04;   z is from 0.05 to 0.5;   r is from 10 -4  to0.01;   y is from 1×10 -4  to 0.1;   e is from 1×10 -5  to 0.01; and   d' is from 1×10 -4  to 0.020.   
     
     
       20. A radiographic image storage panel comprising a support and a fluorescent layer including crystals of said storage phosphor of claim 14, said crystals being capable of absorbing X-ray radiation and emitting longer wavelength electromagnetic radiation in response to stimulating radiation of a third wavelength. 
     
     
       21. A storage phosphor consisting essentially of a combination of species characterized by the relationship:   (Ba.sub.1-a-b-c Mg.sub.a Ca.sub.b Sr.sub.c)FX.sub.1-z I.sub.z.rM.sup.a X.sup.a :yA:eQ:tD:d'S     wherein   X is selected from the group consisting of Cl and Br, and combinations thereof;   M a  is selected from the group consisting of Na, K, Rb and Cs, and combinations thereof;   X a  is selected from the group consisting of F, Cl, and Br, and combinations thereof;   A is selected from the group consisting of Eu, Ce, Sm, and Tb, and combinations thereof;   Q is selected from the group consisting of BeO, MgO, CaO, SrO, BaO, ZnO, Al 2  O 3 , La 2  O 3 , In 2  O 3 , SiO 2 , TiO 2 , ZrO 2 , GeO 2 , SnO 2 , Nb 2  O 5 , Ta 2  O 5 , and ThO 2 , and combinations thereof;   D is selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and combinations thereof;   a+b+c is from 0 to 0.4;   z is from 1×10 -2  to 1;   z' is slightly less than z;   r is from 0 to 0.1;   y is from 1×10 -4  to 0.1;   e is from 0 to 0.1;   t is from 0 to 10 -2  ; and   d' is from 0 to 0.020; said phosphor exhibiting luminescence peaks, upon excitation by a 514.5 nm laser beam, at 573.4, 576.1,580.8, 590.2, 611.7, 616.5, 630.6 nm (all ±0.5 nm).     
     
     
       22. The phosphor of claim 21 further characterized as the product of: maintaining in a slightly oxidizing, slightly reducing, or inert atmosphere at a temperature between about 750° C. and about 950° C. a combination of species substantially characterized by said relationship to produce an intermediate product; and   annealing said intermediate product in an atmosphere having from about 10 to about 200 parts per million of oxygen at a temperature lower than said temperature of said firing and between about 500° C. and about 750° C., for a time sufficient to reduce the erase fraction of said storage phosphor relative to the same phosphor produced without said annealing.